1. Field of the Invention
The present invention relates to an image processing system, an image processing apparatus, an image processing method, and a program suitable for use to combine a computer graphics (CG) image with a captured image in a mixed reality (MR) technique in particular.
2. Description of the Related Art
MR techniques have recently been known as techniques for seamlessly integrating the real world and a virtual world in real time. Among the MR techniques, there is a technique for providing a mixed reality image to a user by using a video see-through head mounted display (HMD). The video see-through HMD includes a built-in video camera, which captures an image of an object substantially coincident with an object observed from the user's pupil position. An image obtained by combining a CG image on the captured image is displayed on a display panel of the video see-through HMD, whereby a mixed reality space is provided to the user.
A method using a feature point detected from the captured image and a measurement result of a position and orientation of the video see-through HMD is known as a technique for determining the position to combine the CG image. For performing highly accurate positioning, a greater number of feature points need to be captured with higher definition. For that purpose, the video see-through HMD desirably obtains the captured image with high resolution having a wider viewing angle. In the MR techniques, a high-resolution captured image with a wide viewing angle and a high-resolution display image are also desired for providing a realistic and dynamic feeling to a user. A video see-through HMD typically has an imaging viewing angle similar to a display viewing angle. Japanese Patent Application Laid-Open No. 2010-92436 discusses a method for making the imaging viewing angle wider than the display viewing angle to capture feature points in a wider range, and clipping a partial area of the captured image to generate a display image.
According to the method discussed in Japanese Patent Application Laid-Open No. 2010-92436, more feature points can be imaged by widening the imaging viewing angle. The wider viewing angle, however, lowers the resolution per pixel. To accurately measure the position and orientation, resolution of the captured image needs to be increased as the viewing angle widens. The processing load of processing for detecting feature points from a captured image is typically high. The use of the high-resolution captured image increases the system load.